Most vehicles are now equipped with an audio system: commonly this is already installed in new vehicles as original factory installation. It is not unusual for a vehicle to be equipped with four or more speakers. Since space is usually restricted, compact door-mounted speakers are popular. The present invention is directed to compact speakers having a circular outline, as opposed to an elliptical or square outline.
Two predominant types of compact circular speakers that are widely used in vehicles are close in size: 6.5" nominal (165 mm) associated largely with Asian-produced vehicles and with Japanese industry JIS standards, and 170 mm nominal (6.7") associated largely with European-produced vehicles and with DIN standards. Many American-produced as well as imported vehicles are made with compact round speaker mounting cutout/hole patterns of one or other of these two types, depending on the vehicle make and year.
Although these two types are close in size, the dimensional differences in mounting patterns are such as to ordinarily prevent interchangeability between the two speaker types. Furthermore, since the 170 mm type has about 14% larger cone area than the 6.5" type, it is considered superior for bass frequency performance capability since its larger cone produces a given SPL (sound pressure level) with a shorter travel and therefore requires less clearance to prevent the diaphragm system from "bottoming" at low bass frequencies. Thus any purely mechanical adaptation of the smaller speaker that is presently known and/or available for replacing the larger speaker would fail to duplicate its inherently higher performance capability.
The manner of mounting speakers in vehicles is important both in original vehicle manufacturing, where rapid and easy installation on the assembly line is of great importance for the labor cost savings, and in vehicle sound servicing where both installation and removal of a speaker represent time and cost expenditures.
The most common speaker locations in vehicles is in the side doors where typically speakers are mounted onto the interior sheet metal panel, extending into the door compartment; rear speakers can be located in a bulkhead panel behind the rear seat cushion, where they are typically mounted to the rear of the bulkhead panel, facing forwardly in the vehicle.
Typically, circular speakers are made with an array of mounting holes located just inside the rim for fastening the speaker in place with a set of mounting screws. If the mounting panel is of sheet metal, these mounting screws are typically self-tapping screws driven into suitably sized round holes; alternatively the holes may be extruded and threaded to accept machine screws. In either case, installation and removal are relatively easy and labor-efficient when no fastening hardware is required on the reverse side of the mounting panel.
However where fastening hardware is required on the reverse side, e.g. where the mounting panel material is unsuitable for reliably threading or engaging self-tapping screws, such assembly tends to be slow and costly: since the main opening is occupied by the speaker itself, lack of rear accessibility may require two workers to install or remove the speaker.
In a compact speaker for the automobile marketplace, bass performance capability is a key parameter, also the product must be easily mountable into the standard speaker openings provided in popular vehicle models. It is highly desirable to minimize the number of different sized speakers that need to be produced; for example it would be a manufacturing and distributing economy to provide a single versatile speaker type that could be mounted in standard speaker mounting cutouts of either the 6.5" or the 170 mm type. The versatile speaker type would require a cone size that would provide the performance of the 170 mm unit; this would provide a performance bonus in the 6.5" applications.
To suspend the edge of the cone, it is conventional practice to provide a surround suspension member having an arched resilient portion with its inner edge attached to the cone edge and its outer edge extended in the form of a surround suspension mounting flange which is adhesively attached to the rim portion of the speaker frame, typically via a spacer ring.
In contemplating speakers as candidates for OEM (original equipment manufacture) of automobiles or as an OEM replacement, it is a ground rule that there can be no physical modification of the speaker mounting panel, assuming it is part of a vehicle, such as drilling, cutting, bending etc., since such would void the vehicle warranty.